Lens

Located just behing the iris, the lens is one of the components that determine how the eye is focused, and is also responsible for focusing the eye to see near objects. As we age, the lens becomes increasingly dense and inflexible, causing a continual decrease in the eye's focusing ability, known as presbyopia. The lens can develop cataract as a result of age or injury, or it can be present at birth.

Iris

This is the ring-shaped colored part of your eye, and is responsible for
controlling the amount of light that enters the eye. In the light, the iris constricts to make the opening in the iris, the pupil, smaller to decrease the amount of light entering the eye. In the dark, the iris dilates, increasing the pupil size and allowing more light to enter the eye.

Cornea

This is the clear dome over the iris, and is on average just 1/2 mm thick. The cornea is one of the components that determine how the eye is focused. Contact lenses are worn on the cornea, and this is also where laser refractive surgery is performed.

Pupil

This is the circular opening in the centre of the iris, and changes size in different lighting conditions. The pupil is normally black, but if the eye is lit up inside, such as when a camera flash goes off, the color of the interior of the eye will be visible and the pupil will appear red.

Aqueous

This fluid fills the area between the cornea and the lens, and is continually produced and continually drained.
The amount of aqueous in the eye determines the eye pressure, which varies at different times and on different days. If the eye pressure is too high for the eye tissues to tolerate, glaucoma can develop.

Conjunctiva

This is a thin layer of transparent tissue that covers the white of the eye, the sclera. The conjunctiva contains many blood vessels, which fill with blood and expand if the eye is irritated, making the eye appear red.

Sclera

This is the white, tough outer casing of the eye, which gives the eye its shape and strength to resist damage.

Vitreous

This jelly-like fluid fills the area between the lens and the retina. Often the vitreous contains fibers or clumps which are seen as shifting black or translucent shapes in the vision, called floaters. It is normal to notice an increase in floaters over time. The vitreous is contained within a capsule, which is attached to the retina at multiple points. At some point in life, usually in the 50s or 60s, the capsule of the vitreous pulls away from the retina and collapses into itself, much like a balloon deflating. This is called a vitreous detachment, and is a normal part of aging.

Retina

This thin layer of tissue lines the inside of the eyeball, and contains cells that receive light and transfer it into visual messages that are sent to the brain via the optic nerve. The retina also contains many blood vessels, which, as a result of various eye conditions or disesases, can break and bleed, causing vision loss. A retinal detachment occurs if the retina loses its attachment to a part of the eyeball, allowing it to come away from the wall of the eye.

Macula

This is an area in the central part of the retina, which provides detailed vision. Diseases or injury affecting this area will almost always cause noticeable vision loss. One of the most common diseases that affects this part of the retina is macular degeneration.

Optic Nerve

This nerve carries visual messages from the retina to the brain, which interprets the messages, resulting in the perception of vision. Glaucoma damages the optic nerve, causing individual nerve fibers to gradually die off, resulting in a subtle but progressive loss of vision.